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Chapter 2. Scientific Method. Scientific Method. Scientific method- logical approach to solving problems by observing & collecting data, formulating hypotheses, testing hypotheses, formulating theories supported by data Examples of problems… Observable data

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chapter 2

Chapter 2

Scientific Method

scientific method
Scientific Method
  • Scientific method- logical approach to solving problems by observing & collecting data, formulating hypotheses, testing hypotheses, formulating theories supported by data
  • Examples of problems…
  • Observable data
    • Qualitative = descriptive (turn pink)
    • Quantitative = numerical (1 gram)
slide3
Data
  • We cannot observe everything all at once, so we focus on a system
  • System- specific portion of matter chosen for study (ex. Reaction in a test tube)
  • Once we obtain data, we can establish patterns
  • Patterns can be made into scatter plots, bar graphs, pie charts, etc.
hypothesis
Hypothesis
  • Once we have looked for patterns, we form a hypothesis
  • Hypothesis- testable statement in the form of “if…then…”
  • Then we have to test the hypothesis
    • Control(s)- stay constant (placebo)
    • Variable(s)- change, only changed one at a time
    • If wrong, change or drop hypothesis (might start over)
hypothesis con
Hypothesis (con.)
  • If correct, explain through models
  • Model- explains how events occur or are related in a visual, verbal, or mathematical way
  • Theory- broad generalization that explains group of facts or events
  • Publish results (letters, scholarly journals, blog, word of mouth)
metric system
Metric System
  • SI, or SystèmeInternationaled’Unités (French)
  • Base units
    • Length (lowercase L) = meter (m)
    • Mass (m) = kg (kilogram)
    • Time (t) = second (s)
    • Temperature (T) = Kelvin (K)
    • Amount of substance (n) = mole (mol)
    • Electric current (I) = ampere (A)
    • Luminous intensity (Iv) = candela (cd)
metric prefixes
Metric prefixes
  • Mega (M) = 10 6
  • Kilo (k) = 10 3
  • Hecto (h) = 10 2
  • Deka (da) = 10 1
  • Deci (d) = 10 -1
  • Centi (c) = 10 -2
  • Milli (m) = 10 -3
  • Micro (µ) = 10 -6
  • Practice problems on board
mass vs weight
Mass vs. Weight
  • Mass = amount of matter
  • Weight = amount of gravity pull
  • On moon, gravity 1/6 that of Earth
  • Didn’t lose mass, lost weight
derived si units
Derived SI units
  • Combinations of base units
  • Area (A) = lxw = m2 or cm2
  • Volume (V) = lxwxh = m3 or cm3
  • Density (D) = kg/m3 or g/cm3 or g/mL
  • Molar Mass (MM) = kg/mol
  • Energy (E) = Joule (J)
accuracy vs precision
Accuracy vs. Precision
  • Accuracy- close to accepted value
  • Precision- close to measurements made in same way
  • Drawings on board
percent error
Percent Error
  • Goal = 0
  • (Experimental – Accepted)/(Accepted) x 100
  • Problems on board
significant figures
Significant figures
  • All digits but last one certain
  • Rules
    • Nonzero = significant
    • Zero in between nonzero (2002) = significant
    • Zero in front of nonzero = not significant
    • Zero at end of number and to right of decimal = significant
    • Ex. 2000 = 1 sig, 25.00 = 4 sig, .0001 = 1 sig
    • Examples on board
rounding
Rounding
  • 1->4, round down
  • 6->9, round up
  • 3.5->4
  • 4.5->4
  • Sig + or – Sig= same # of decimals
  • Sig x or / Sig = same # of sig digits
  • Examples on board
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